stroker; how to?

I'm looking to build a stroker motor for my 87 comanche. the truck is a shortbed, lifted 6.5", automatic aw4 with a 4.0, np231 with SYE, dana 44 rear and 4.10 gears
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here's what I'm looking for...high power and torque, with the ability to get great gas mileage. i know if you're light-footed on a 4.0 stroker you can get upwards of 25mpg, and that's what I would like to achieve.

basically here are my options...

I've got a 1989 4.0 with 150k miles, an 88 4.0 with 101k miles, and a 2001 4.0 with who knows miles but a cracked piston.

one 93 H.O. head and intake, and a borla exhaust manifold for that.

I'm trying to figure out what all I will need to build a stroker motor. I know i will need a YJ crank and have it machined to fit the 4.0 harmonic balancer. I'm intending to use the 4.0 connecting rods with some performance pistons (shorter) to make up the length difference.

not sure on what bore... thinking .030 or so.

any opinions on cams?

opinions on which motor to base this off of? I don't want to deal with wiring swaps right now, as this engine will need to be built dropped in then running within a day or two of yanking the old motor.

also, any changes that would need to be made to the computer?

the project will be a fall/winter project then dropped into the truck.

oh, and my budget is less than 1500 bucks.

jeepcomj said:

oh, and my budget is less than 1500 bucks.

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Good luck. :thumbup:

Use whichever block you please as long as it's older than 1990. That's the last of the RENIX era which is what your MJ is. Get it machined .030 over for a 4.6L and .060 for a 4.7L (cylinder bore that is). Then get a crankshaft with the 3727 cast # on it, it wont have to be machined and it will have better MPG cause its lighter. Gather some pistons, rings etc to go with your 4.2L crank and rods. Get a $120 comp cam or just reuse your stock one. New injectors are in order as well. There are alot of stroker threads out there....just search.

Use the HO head and Borla exhaust, might wanna throw on a 62mm throttle body and a K&N, really it all depends on what you want. The most costly thing can be the crank, however I just bought a complete 4.2L for $100 and got the crank/rods machined for a total of $175 on the crank/rods cost.


http://www.ajeepthing.com/stroker-motor.html


Check this page, do some research and get an excel sheet going for a project total. You're gonna have to comprimise here and there to get what you want and budget your money well, but it can def be done under $1500. Mine cost around $1000+/-.


You just have to read, decide what you want, and price things.....shop around. Customer loyalty is nice, but they don't know when you go other places for certain things.

It's the exact some thing as an engine rebuild, but you sway out the 4.2 crank and rods.

If you really wanted to get squirrely with it, you could buy this $600 forged pistons from Hesco ( www.hesco.us ) and price other things around that. Talk to Benny, but they really don't fuck around with their parts since no one makes these cranks/rods anymore. If they got them they're gonna keep them.

If you have anymore questions after some RESEARCH OF YOUR OWN, then ask.

--Alex

EDIT: I understand that you need an adjustable MAP sensor. I am putting my stroker in today (God willing) and I havent gotten that far.

Keith Black now makes twp different forged pistons for jeep strokers. It is designed to use the 4.2 crank and the 4.0 rods. I've heard alot of different numbers for the price on these things so you should just ask your machinist if they can get you a set.

you might also want to check out www.jeepstrokers.com (read the FAQ section)

~Alex

http://www.lunghd.com/Off_Site_Tech.htm

There's alot of links to pages talking about how to stroke a 4.0 and various parts and methods used.

thanks! especially for the crank #...this is something I was looking for.

I should provide a little bit of background here...the machine work is free as I know a machinest well enough to use his equipment. the motors are all byproducts of trades/deals/projects which have grossed more money than put in, so I consider them free. the 4.2 crankshaft will be next to free if not free, and 4.0 rods are plentiful.

the only things that will really cost me money are the gasket set (less than $200), the pistons, rings, and crank/rod bearings. I've got the proper replacement bolts for the connecting rods, and head bolts, and valve jobs are something I can do.

I need to decide what to do with the rockers and push rods as well as lifters, but I imagine that's a decision that won't need to be made right away (so long as I don't make the mistake of installing the head prior to the lifters.. )

from what I'd read, I'd deduced on using a renix block, with the H.O. head and 2001 intake with borla exhaust.

my spread sheet puts me at (roughly) under $900 in parts thus far...but that's not including lifters or rockers, nor does it include any assembly fluids or sealant.

trust me, I've searched on the subject but wanted input...thank you for your advice.

I would definitely look around on that gasket set. I got mine around $70 from the local. It had every gasket I needed. I spent less than $1000 including machining/cleaning, general parts and even new stuff that I didnt really need like a thermostat, tranny cooler, K&N, etc.

And all I did to do this was SHOPPING AROUND!!!!!

Not too bad, of course your going for the hot-shot pistons. Be sure to get a copy of "Andrea's stroker calculator" and find out what CR and disp. I think it can be found on Muab'dib's stroker site (that name may not be spelled right). I want to see how everything turns out. Let us know.

--Alex

so what is the idea behind using a renix block and why is it better then the ho block?

Renix has a Knock Sensor.

thanks again.

also, renix doesn't have timing that's waaay advanced as it still uses an EGR valve (I will delete mine since swapping to the H.O. head)...hence the fact that renix is capable of higher gas mileage (when/if running properly)

slcpunk74 said:

so what is the idea behind using a renix block and why is it better then the ho block?

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In the renix era's the blocks are rumored to have had thicker cylinder walls too.

cal said:

In the renix era's the blocks are rumored to have had thicker cylinder walls too.

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And a higher Nickle content for more wear resistance. Don't quote me on that but I did hear it. Maybe from 5-90? I dont know it was back when I first got on .
--Alex

thinking of bigger valves now too...this thing may suck more $$$ than I intended it to

Bigger valves are not worth the expense. my machinist said he wouldn' even do the work. Save your money, do a mild port -n- polish.

Frank Z said:

Bigger valves are not worth the expense. my machinist said he wouldn' even do the work. Save your money, do a mild port -n- polish.

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ok

Sorry to thread jack, but can you use a renix block for a build in a later model cherokee with the HO engine? like using a renix block, HO head in a 94?

that's what I have 89 block into a 93 jeep with a 2000 intake for it. The only prolem I ran into was one of the bolt holes in the front coverwas too small for the factory 93 bracket. One of the bolts thatholds the alternator bracket on. And the older block didn't have the holes to mount the coil and ground wires on it. The bosses were there but they weren't drilled and tapped.

So were you able to drill and tap the wholes and make it all work anyways? just turned into a little extra customizing to make it work?

How about wiring harness and all? all the right plugs and everything
?